cm. │479 Foot-pounds │Kilogrammetres │0·1382 „ „ │Joules │1·356 „ „ │Thermal Units │0·00129 „ „ │Calorie │0·000324 Foot-tons │Tonne-metres │0·333 Horse-power │Force decheval (Fr.H.P.) │1·014 „ „ │Kilowatts │0·746 Pounds per H.P. │Kilos. per cheval │0·447 Square feet per H. P. │Square metres per cheval │0·0196 Cubic „ „ │Cubic „ „ │0·0279 Watts │Ther. Units per hour │3·44 „ │Foot-pounds per second │0·73 „ │„ per minute │44·24 Watt-hours │Kilogrammetres │367 „ „ │Joules │3600 Kilogrammetres │„ │9·806 ──────────────────────────┴──────────────────────────┴───────── _Inverse Proportion._—If “more” requires “less,” or “less” requires “more,” the case is one of _inverse_ proportion, and although it will be seen that this form of proportion is quite readily dealt with by the preceding method, the working is simplified to some extent by inverting the slide so that the C scale is adjacent to the A scale. By the aid of the cursor, the values on the inverted C (or Ɔ) scale, and on the D scale, can be then read off. These will now constitute a series of inverse ratios. For example, in the proportion ─────────── Ɔ 8 4 ─────────── D 1·5 3 the 4 on the Ɔ scale is brought opposite 3 on D, when under 8 on Ɔ is found 1·5 on D.[5] GENERAL HINTS ON THE ELEMENTARY USES OF THE SLIDE RULE. Before the more complex operations of involution, evolution, etc., are considered, a few general hints on the use of the slide rule for elementary operations may be of service, especially as these will serve to enforce some of the more important points brought out in the preceding sections. Always use the slide rule in as _direct_ a light as possible. Study the manner in which the scales are divided. Follow the graduations of the C and D scales from 1 to 10, noting the values given by each successive graduation and how these values change as we follow along to the right. Do the same with the two halves of the A and B scales and note the difference in the value of the subdivisions, due to the shorter scale-lengths.